The End Papers, created by artist Sto Len, were produced using naturally occurring water pollution in waterways throughout the world. While visually and emotionally stunning, these are also a preservation challenge due to the unknown components of the pollution in the prints.
(Note: this image was taken through glass, the paper itself is not reflective.)
https://fcaw.library.umass.edu/F/?func=direct&doc_number=016528412&doc_library=FCL01